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International 21
Designer: Helsen  ·  Builder: International Yacht Corp.  ·  First built: 1976
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About the International 21

With limited documentation available, the International 21 represents one of those intriguing smaller sailboats that emerged during an era when builders were exploring various approaches to affordable recreational sailing. This compact vessel appears to have been designed with weekend sailors and smaller crews in mind, making it well-suited for coastal cruising and day sailing adventures. Based on its name and size class, the International 21 likely features a straightforward design philosophy emphasizing simplicity and ease of handling. Boats of this vintage and size typically offered good learning platforms for developing sailors while still providing enough capability for coastal exploration. The modest proportions would have made trailer sailing practical, opening up cruising possibilities beyond a single home port. While comprehensive historical records remain elusive, the International 21 fits into that category of wholesome family sailboats that prioritized accessibility over racing performance. Prospective buyers researching this model should expect a boat that delivers honest sailing characteristics without unnecessary complexity. The design likely emphasizes stability and predictable handling over cutting-edge performance, making it potentially attractive to those seeking a straightforward sailing experience. As with many boats from this era, finding well-maintained examples may require patience and thorough inspection.

Core Dimensions
LOA (Length Overall) 21.50 ft / 6.55 m
LWL (Waterline Length) 17.33 ft / 5.28 m
Beam 7.33 ft / 2.23 m
Max Draft 4.00 ft / 1.22 m
Min Draft 1.16 ft / 0.35 m
Displacement 1,750.00 lb / 794 kg
Ballast 400.00 lb / 181 kg
Sail Area (Reported) 175.00 ft² / 16.26 m²
Design & Construction
Hull Type Swing Keel
Rigging Type Masthead Sloop
Construction FG
Designer Helsen
Builder International Yacht Corp.
First Built 1976
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Performance Ratios
SA/Displacement Sail Area to Displacement ratio measures how much sail power a boat has relative to its weight. Higher values mean more performance and speed.
Under 14 — Heavy cruiser, slow14–18 — Cruising sailboat18–22 — Cruiser/racerOver 22 — Performance racer
19.32
Comfort Ratio Ted Brewer's Comfort Ratio predicts how comfortable a boat will feel in offshore conditions. Higher values mean a steadier, more comfortable motion in a seaway.
Under 20 — Uncomfortably rough20–30 — Acceptable coastal30–40 — Good offshore comfortOver 40 — Very comfortable offshore
10.24
Capsize Screening Formula The USHS Capsize Screening Formula estimates offshore capsize risk. Lower is safer — values under 2.0 are considered acceptable for offshore sailing.
Under 2.0 — Safe for offshore2.0–2.2 — Borderline offshoreOver 2.2 — Coastal use recommended
2.44
Hull Speed Hull Speed is the theoretical maximum speed of a displacement hull, calculated from waterline length. Most cruising sailboats reach this speed in moderate conditions. 5.58
Pounds/Inch Immersion Pounds per Inch Immersion (PPI) tells you how much weight is needed to sink the boat one inch. Useful for calculating how additional gear and stores affect waterline. 453.89
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